Extreme Temperature Responses, Oxidative Stress and Antioxidant Defense in Plants - Abiotic Stress: Plant Responses and Applications in Agriculture - page 181

Figure 3. Sterile spikelets of rice due to cold stress
3.4. Cell membrane damage
Extreme temperature injuries caused either by cold or by HT first attack on the cell membrane.
There are many studies where cellular membranes have been shown as the primary site of
freezing injury in plants [121, 122]. Cell membrane is damaged in two ways viz. disruption of
protein lipid structure, protein denaturation and precipitation of solutes that indulges the
membrane permeability. Due to LT stress the fatty acids become unsaturated and the lipid
protein ratios of the membrane become altered which ultimately affect the membrane fluidity
and structure as well [90]. The flexible liquid-crystalline phase is converted in to a solid gel
phase, thereby affecting the cellular function in different ways, viz. increased membrane
permeability increases ion leakage, allows the entrance of undesirable anions and cataions into
the cell, obstructs the exchange of essential ions, hampers the osmosis and diffusion processes,
etc. All the phenomena are responsible for disrupting cellular homeostasis [97]. Conversion of
cellular water into ice is a major reason for cell rupture in cold stress. At first the ice formation
occurs in apoplast having low solute concentration, this creates a vapor pressure between
cytoplasm and apoplast and results in the migration of unfrozen cytoplasmic or cytosol water
to the apoplast. This water gives a pressure which is the cause of enlargement of existing ice
crystals and the pressure towards the cell wall and cell membrane which leads to cell rupture
[123, 124].
3.5. Photosynthesis
Low temperatures may disturb the key organs of photosynthesis, including chloroplast and
thylakoid membranes, causes swelling of plastids and thylakoid lamellae, vesiculation of
thylakoid, accumulation of lipid drops and ultimately disorganization of entire plastid [111,